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[CodeGen] Fix generation of TBAA info for array-to-pointer conversions 

Resolves:
Fatal error: Offset not zero at the point of scalar access.
http://llvm.org/PR34992

Differential Revision: https://reviews.llvm.org/D39083

llvm-svn: 316211
This commit is contained in:
Ivan A. Kosarev 2017-10-20 12:35:17 +00:00
parent 3d34d877cb
commit f761d0e514
2 changed files with 26 additions and 2 deletions
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10
clang/lib/CodeGen/CGExpr.cpp
View File

@ -3072,8 +3072,6 @@ Address CodeGenFunction::EmitArrayToPointerDecay(const Expr *E,
// Expressions of array type can't be bitfields or vector elements.
LValue LV = EmitLValue(E);
Address Addr = LV.getAddress();
if (BaseInfo) *BaseInfo = LV.getBaseInfo();
if (TBAAInfo) *TBAAInfo = LV.getTBAAInfo();
// If the array type was an incomplete type, we need to make sure
// the decay ends up being the right type.
@ -3088,7 +3086,15 @@ Address CodeGenFunction::EmitArrayToPointerDecay(const Expr *E,
Addr = Builder.CreateStructGEP(Addr, 0, CharUnits::Zero(), "arraydecay");
}
// The result of this decay conversion points to an array element within the
// base lvalue. However, since TBAA currently does not support representing
// accesses to elements of member arrays, we conservatively represent accesses
// to the pointee object as if it had no any base lvalue specified.
// TODO: Support TBAA for member arrays.
QualType EltType = E->getType()->castAsArrayTypeUnsafe()->getElementType();
if (BaseInfo) *BaseInfo = LV.getBaseInfo();
if (TBAAInfo) *TBAAInfo = CGM.getTBAAAccessInfo(EltType);
return Builder.CreateElementBitCast(Addr, ConvertTypeForMem(EltType));
}

18
clang/test/CodeGen/tbaa-array.cpp Normal file
View File

@ -0,0 +1,18 @@
// RUN: %clang_cc1 -triple x86_64-linux -O1 -disable-llvm-passes %s \
// RUN: -emit-llvm -o - | FileCheck %s
//
// Check that we generate correct TBAA information for accesses to array
// elements.
struct A { int i; };
struct B { A a[1]; };
int foo(B *b) {
// CHECK-LABEL: _Z3fooP1B
// CHECK: load i32, {{.*}}, !tbaa [[TAG_A_i:!.*]]
return b->a->i;
}
// CHECK-DAG: [[TAG_A_i]] = !{[[TYPE_A:!.*]], [[TYPE_int:!.*]], i64 0}
// CHECK-DAG: [[TYPE_A]] = !{!"_ZTS1A", !{{.*}}, i64 0}
// CHECK-DAG: [[TYPE_int]] = !{!"int", !{{.*}}, i64 0}